Fix some typos and grammar issues from commit 87985cc

Reported-by: Alexander Lakhin

Author: akorotkov

src/backend/access/heap/heapam.c

@@ -3412,7 +3412,7 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
 
 		/*
 		 * If we're asked to lock the updated tuple, we just fetch the
-		 * existing tuple.  That let's the caller save some resouces on
+		 * existing tuple.  That lets the caller save some resources on
 		 * placing the lock.
 		 */
 		if (result == TM_Updated &&

src/backend/commands/trigger.c

@@ -2784,8 +2784,8 @@ ExecARDeleteTriggers(EState *estate,
 		(transition_capture && transition_capture->tcs_delete_old_table))
 	{
 		/*
-		 * Put the FDW old tuple to the slot.  Otherwise, caller is expected
-		 * to have old tuple alredy fetched to the slot.
+		 * Put the FDW old tuple to the slot.  Otherwise, the caller is
+		 * expected to have an old tuple already fetched to the slot.
 		 */
 		if (fdw_trigtuple != NULL)
 			ExecForceStoreHeapTuple(fdw_trigtuple, slot, false);